OCR Chemistry Revision - The Basic Things You Need To Know. OCR Chemistry Revision - Calculations and Exam Questions. Question 1 - Part 1 (2 marks): 'Calcium carbonate, CaCO3, reacts with nitric acid, HNO3. A student neutralised 2.68g of CaCO3 with 2.50 mol dm-3 nitric acid, HNO3.The equation for this reaction is shown below: CaCO3(s) + 2HNO3(aq)-> Ca(NO3)2(aq) + CO2 + H2O Determine the amount, in mol, of CaCO3 reacted.' Using the formula above for calculating the moles of a solid compound, we need to divide the mass by the molecular formula mass (Mr).Add up the atomic masses of Ca (40.1), C (12) and 3 O's (16 x 3): 40.1 + 12 +16 + 16 + 16 = 100.1Now divide the mass of CaCO3by the Mr that you just calculated:2.68 ÷ 100.1 = 0.0268.The amount of CaCO3 reacted was 0.0268 mol.
OCR Chemistry Revision - Calculations and Exam Questions. AS Chemistry - Chemical Bonding. Definition of ionic bond:'The electrostatic attraction between two oppositely charged ions.' Ionic bonding occurs between the atoms of a compound consisting of a metal and a non-metal. The electrons of the metal atom are transferred to the non-metal atom and this forms oppositely charged ions (a positive metal ion and a negative non-metal ion). These ions are then bonded together by electrostatic attraction, otherwise known as an ionic bond.
Take the compound sodium oxide (Na2O) for example. The sodium atoms then form Na+ ions (because they have lost an electron) and the oxygen atom forms an O2− ion (because it has gained 2 electrons). The electrostatic attraction between these oppositely charged ions forms an ionic bond. However, the two Na+ ions and the one O2− ion were not the only ions involved in the ionic bonding. The attraction of all of these ions forms a giant ionic lattice structure. OCR Chemistry Revision - The Basic Things You Need To Know.